1. Field of the Invention
The present invention relates to dipole antennas, more specifically it relates to adjustable dipole antennas.
2. Description of the Related Art
In the past, adjustable dipole antennas were fabricated using telescoping antenna elements that extended in opposite directions. The antennas were adjusted to a specific frequency by adjusting the lengths of the telescoping antenna elements. Using adjustable dipole antennas that comprised telescoping antenna elements have several draw backs. When the antenna is adjusted to receive low frequency signals, the antenna elements must be extended to relatively long lengths. Due to the weight of a telescoping element structure, the ends of the antenna elements tended to droop when extended out for low frequency operation. This drooping adversely effected the antenna's performance. In addition, long antenna elements adversely effected antenna performance by swaying in the wind.
An antenna element using a telescoping construction can only be adjusted over a limited range. For example, the antenna cannot be adjusted to a length which is shorter than the first section of the telescoping structure. This limitation requires using a variety of telescoping elements when the adjustable dipole antenna is intended for use over a wide range of frequencies.